Recommended minimum scrotal circumference for tropically-adapted beef bulls in northern Australia

McGowan, M., Muller, T., Lisle, A., Fordyce, G., Holroyd, R. and Doogan, V. (2012). Recommended minimum scrotal circumference for tropically-adapted beef bulls in northern Australia. In: Special Issue: Proceedings of the 17th International Congress on Animal Reproduction (ICAR). 17th International Congress on Animal Reproduction (ICAR), Vancouver Canada, (519-519). 29 July - 2 August 2012.


Author McGowan, M.
Muller, T.
Lisle, A.
Fordyce, G.
Holroyd, R.
Doogan, V.
Title of paper Recommended minimum scrotal circumference for tropically-adapted beef bulls in northern Australia
Conference name 17th International Congress on Animal Reproduction (ICAR)
Conference location Vancouver Canada
Conference dates 29 July - 2 August 2012
Proceedings title Special Issue: Proceedings of the 17th International Congress on Animal Reproduction (ICAR)   Check publisher's open access policy
Journal name Reproduction in Domestic Animals   Check publisher's open access policy
Place of Publication Berlin, Germany
Publisher Wiley-Blackwell
Publication Year 2012
Sub-type Published abstract
ISSN 0936-6768
1439-0531
Volume 47
Issue s4
Start page 519
End page 519
Total pages 1
Language eng
Abstract/Summary Scrotal circumference has long been regarded as a readily-measured indicator of beef bull fertility and is therefore routinely included in bull breeding soundness examinations. However, concerns have been raised that current minimum thresholds for tropically adapted genotypes do not account for the large variations in northern Australia bull nutrition. The primary objectives of this study were to examine the interaction and effects of weight and age on scrotal circumference and to develop minimum thresholds indicative of suboptimal testicular development. Scrotal circumference measurements (n = 9300) from 1958 bulls £3 years of age, were analysed. Breeds included Brahman (n = 559), Droughtmaster (n = 133), Santa Gertrudis (n = 460) and other tropical composites (n = 806). The bulls were located on multiple sites across Queensland, and most continuously grazed native or improved pastures of varying quality, with some receiving commonly-used supplements. Some bulls were lot fed for a period to achieve growth rates of approximately 1 kg/day. Both weight (r = 85.8%) and age (r = 78.5%) had significant positive correlations with scrotal circumference. The Gompertz function, a relatively common non-linear model used to describe growth, best described testicular development in relation to weight in all breeds (R2 = 80.4). Breed differences in testicular development were small, although tropical composite bulls matured at a slightly earlier age/weight than the other breeds studied. The minimum recommended scrotal circumference within weight ranges were derived for field use as less than the lower 5th percentile (Table 1).
Keyword Testis
Scrotal circumference
Bovine
Nutrition
Bull
Q-Index Code CX
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Abstract 1902

 
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